Prussia was a German kingdom and historic state originating out of the Duchy of Prussia and the Margraviate of Brandenburg, and centered on the region of Prussia. For centuries, the House of Hohenzollern ruled Prussia, successfully expanding its size by way of an unusually well-organised and effective army. Prussia, with its capital in Berlin after 1451, shaped the history of Germany. In 1871, German states united in creating the German Empire under Prussian leadership. In November 1918, the monarchies were abolished and the nobility lost its political power. Prussia was effectively abolished in 1932, and officially abolished in 1947.

Prussia entered the ranks of the great powers shortly after becoming a kingdom, and exercised most influence in the 18th and 19th centuries. During the 18th century it had a major say in many international affairs under the reign of Frederick the Great. During the 19th century, Chancellor Otto von Bismarck united the German principalities into a "Lesser Germany" which excluded the Austrian Empire.

At the Congress of Vienna (1814–15), which redrew the map of Europe following Napoleon's defeat, Prussia acquired a large section of north western Germany, including the coal-rich Ruhr. The country then grew rapidly in influence economically and politically, and became the core of the North German Confederation in 1867, and then of the German Empire in 1871. The Kingdom of Prussia was now so large and so dominant in the new Germany that Junkers and other Prussian élites identified more and more as Germans and less as Prussians.

The Kingdom ended in 1918. In the Weimar Republic the state of Prussia lost nearly all of its legal and political importance following the 1932 coup led by Franz von Papen. East Prussia lost all of its German population after 1945, as Poland and the Soviet Union absorbed its territory.

The term "Prussian" has often been used, especially outside of Germany, to emphasise the professionalism, aggressiveness, militarism and conservatism of the Junker class of landed aristocrats in the East who dominated first Prussia and then the German Empire before 1918.

The Hanseatic League was officially formed in northern Europe in 1356 as a group of trading cities which came to have a monopoly on all trade leaving the interior of Europe and Scandinavia and on all sailing trade in the Baltic Sea for foreign countries. The businessmen of the interior Sweden, Denmark and Poland came to feel oppressed by the Hanseatic League.

In the course of the Ostsiedlung process settlers were invited, bringing changes in the ethnic composition as well as in language, culture and law. As a majority of these settlers were Germans, Low German became the dominant language.

The Knights were subordinate to the pope and the emperor. Their initially close relationship with the Polish Crown deteriorated after they conquered Polish-controlled Pomerelia and Danzig (Gdańsk) in 1308. Eventually Poland and Lithuania, allied through the Union of Krewo (1385), defeated the Knights in the Battle of Grunwald (Tannenberg) in 1410.

In 1525, Grand Master Albert of Brandenburg-Ansbach, a member of a cadet branch of the House of Hohenzollern, became a Lutheran Protestant and secularised the Order's remaining Prussian territories into the Duchy of Prussia. This was the area east of the mouth of the Vistula River, later sometimes called "Prussia proper." For the first time, these lands came into the hands of a branch of the Hohenzollern family. (The Hohenzollern dynasty had ruled the Margraviate of Brandenburg to the west, a German state centred on Berlin, since the 15th century.) Furthermore, with his renunciation of the Order, Albert could now marry and produce legitimate heirs.